Red-Emitting Ru(II) Metal–Ligand Complexes

A series of Ru(N–N)₂(dcbp or mcmabp) complexes were synthesized where N-N represents a diimine ligand, dcbp is 4,4-dicaboxylic 2,2-bipyridine, and mcmabp is 4,4-2,2-bipyridine monocarboxy amide. The N-N ligand was either 2,2-bipyridine (bpy), 4,4-dimethyl-2,2-bipyridine (dmbp), or 4,4,5,5-tetramethyl-2,2-bipyridine (tmbp). We observed a red shift in both the absorption and emission with the presence of dcbp in the mixed ligand complex when compared to Ru(bpy)₃. Conversion of one of the carboxylic groups in dcbp to amide resulted in further red shifts. A red shift in the absorption and the emission was also observed with increasing numbers of electrons donating methyl substitutions on bpy. The lifetimes of the complexes decreased as expected with the red shift emission. The tris heteroleptic Ru (tmphen)(tmbp)(dcbp or mcmabp) were the most red-shifted among the complexes. Because of the red shift in the absorption, the maxima in the fundamental anisotropies of the mixed ligand Ru complexes are now coincident with the maxima in the absorption. Overall we have been able to make an Ru complex which emits at about 700 nm in all aqueous environment and has a lifetime of about 220 ns.     

Characteristics of Surface Spin Waves in a Metal–Dielectric–Ferrite–Dielectric–Metal Structure

The dispersion and isofrequency characteristics of surface spin waves in a tangentially magnetized metal–dielectric–ferrite–dielectric–metal structure are investigated. A loop-like change in the isofrequency dependences for spin waves is observed in a certain range of frequencies, and the origin of the loop is always located at wave number value k → 0.     

Microdischarges Near Metal–Insulator Interfaces

Some statistical features of microdischarges running near the metal-insulator interfaces have been discussed. The study has verified an exponential character of statistical distributions of the time intervals between microdischarge pulses, power-law distribution of voltage peaks of these pulses (height of pulses) and very weak correlation effects among pulses, i.e. weak time-height correlation, time autocorrelation and height autocorrelation. A statistical parameter of the power law distribution of the heights of microdischarge pulses proved to be sensitive to the voltage load of the insulating interface metal-insulator.     

Metal–insulator transition in Si–MOS structures

A survey is presented on recent investigations of the metal-to-insulator transition in two-dimensional systems with special emphasis on n-Si–MOS structures. Experimental facts are presented and the currently open questions on the nature of this transition are addressed.     

Energy Content of HMX–Silicon Nanopowder Mixtures

Detonation calorimetry studies have shown that the addition of a silicon nanopowder (n-Si) to HMX leads to a significant increase in the heat of explosion. However, the heat of explosion of composites with n-Si is lower than that of composites containing boron and aluminum (particularly aluminum nanoparticles). Combustible additives have been arranged in orders taking into account their effect on the energy content of the explosive.     

Silicon–germanium nanostructures for on-chip optical interconnects

Silicon–germanium epitaxially grown on silicon in the form of two-dimensional (quantum wells) and three-dimensional (quantum dots) nanostructures exhibits photoluminescence and electroluminescence in the technologically important spectral range of 1.3–1.6 μm. Until recently, the major roadblocks for practical applications of these devices were strong thermal quenching of the luminescence quantum efficiency, and a long carrier radiative lifetime. This paper summarizes recent progress in the understanding of carrier recombination in Si/SiGe nanostructures and presents a potential new route toward CMOS compatible light emitters for on-chip optical interconnects.     

Control of Properties of Diamond-Like Silicon–Carbon Films

Physics of the Solid State - The possibilities of control of the electrophysical and mechanical properties of amorphous diamond-like silicon-carbon films by means of structural, chemical and...     

Traps in the Nanocomposite Layer of Silicon–Silicon Dioxide and Their Effect on the Luminescent Properties

Physics of the Solid State - The traps of charge carriers in thermal films of silicon dioxide and silicon dioxide with a nanocomposite layer consisting of silicon oxide and silicon nanocrystallites...     

Negative Differential Resistance and Other Features of Spin-Dependent Electron Transport in Double-Barrier Hybrid Superconductor–Ferromagnetic Metal–Normal Metal Structures

Spin-dependent electronic transport is theoretically investigated for double-barrier hybrid structures S–IF–F–IF–N and S–IF–N–IF–N, where S is a superconductor; F and N are ferromagnetic and normal metals, respectively; and IF is the spin-active barrier. It is shown that in the case of strong superconducting proximity effect and sufficiently thin F layers, the differential resistance of such structures can become negative at some voltages, and the voltage dependence of the current can have an N-shaped form. Characteristic feature of the differential resistance is its asymmetric dependence on voltage, which is most clearly manifested at strong polarization of at least one of the barriers. The influence of impurity spin–orbit scattering processes in the N-layer located between the barriers is investigated. The study was carried out for the case of diffusion electron transport.     

Metal–insulator transition in boron-doped amorphous carbon films

Boron-doped amorphous graphite-like carbon (GLC) films have been prepared with different boron concentrations. Electrical transport measurements in the temperature range 1.3–300?K on the films shows a doping-induced metal–insulator (MI) transition. On the metallic side of the transition, the experimental data are interpreted in terms of weak localization and the effect of electron–electron interactions. Data on the insulator side of transition are analyzed in terms of hopping conduction. Critical behaviour is observed near the transition, with the resistivity obeying a power-law temperature dependence.     

Field-Induced Metal–Insulator Transition in β-EuP_3

Metal-insulator transition(MIT) is one of the most conspicuous phenomena in correlated electron systems.However such a transition has rarely been induced by an external magnetic field as the field scale is normally too small compared with the charge gap.We present the observation of a magnetic-field-driven MIT in a magnetic semiconductor β-EuP_3.Concomitantly,we find a colossal magnetoresistance in an extreme way:the resistance drops billionfold at 2K in a magnetic field less than 3T.We ascribe this striking MIT as a field-driven transition from an antiferromagnetic and paramagnetic insulator to a spin-polarized topological semimetal,in which the spin configuration of Eu~(2+)cations and spin-orbital coupling play a crucial role.As a phosphorene-bearing compound whose electrical properties can be controlled by the application of field,β-EuP_3 may serve as a tantalizing material in the basic research and even future electronics.     

Synthesis and Reactivity of Mg(II)–Fe(II)–Fe(III) Hydroxycarbonates

Green rust-like compounds (GRs) were discovered as natural minerals in various hydromorphic soils, where anoxic conditions allow their stability. They may control some redox processes in aquifers and participate to the transformation of various pollutants. Since Mg(II) cations are present in the fields where GRs were discovered, a partial substitution of Mg(II) to Fe(II) leading to intermediate compounds between GRs and usual Mg(II)–Fe(III) hydroxysalts is suspected. Mg(II)–Fe(II)–Fe(II) hydroxycarbonates can be obtained as intermediate oxidation products of (Mg, Fe)(OH)₂ in carbonate-containing aqueous media obeying to [Fe^II _4(1–x)Mg^II _4x Fe^III ₂(OH)₁₂]²⁺ [CO₃ ^2– nH₂O]^–2. TMS spectra at 12 K are similar to those of GRs, i.e., two quadrupole doublets, one due to Fe(II) with a large isomer shift =1.29 mms^–1 (with respect to -iron at room temperature) and quadrupole splitting E _Q=2.76 mms^–1, the other one due to Fe(III) with smaller hyperfine parameters =0.49 mms^–1 and E _Q=0.44 mms^–1. Fe(II) ions oxidise rapidly into Fe(III) with dissolved O₂. The reactivity is similar to that of Fe(II)–Fe(III) hydroxysalts GR, and thus the potential of Mg(II)–Fe(II)–Fe(III) compounds for reducing pollutants.     

Josephson Tunnel Junctions with an Integral Superconductor–Insulator–Normal Metal Shunt

Physics of the Solid State - This study is devoted to the investigation of tunneling superconductor–insulator–superconductor (SIS) Josephson junctions with a new type of shunt based on...     

Silicon–Platinum Silicide Schottky Barriers with a Highly-Doped Surface Layer

The spectral characteristic of infrared silicon–platinum silicide Schottky barrier photodetectors is shifted to the long wavelength region due to a highly-doped surface silicon layer produced by recoil boron implantation. The dependence of the resulting highly-doped layer parameters on high-energy boron-ion implantation regimes is studied experimentally. Energy-band diagrams and reduction of the barrier height are calculated for p-Si–PtSi structures with highly-doped surface layers produced by molecular-beam epitaxy and recoil implantation.     

Metal–Graphene Hybrid Chiral Metamaterials for Tunable Circular Dichroism

In the field of optoelectronics, circular dichroism (CD) has caused great research interest because it is widely used in imaging and biosensing. A new method for dynamically controlling terahertz (THz) CD in metamaterials is proposed. By introducing chirality and graphene to metamaterials, a pair of chiral structures with completely opposite responses to left-handed circularly polarized (LCP) waves and right-handed circularly polarized (RCP) waves are designed. The influencing factors of CD are explored, including the gap of the structure, the linewidth of graphene, and the Fermi level of graphene. The largest CD (ΔR) is 77%. The CD can be actively modulated in a modulation range of 39–77% and the modulation depth is up to 38%. In addition, two-channel and four-channel chiral metasurfaces for near-field imaging are designed in this way. Good imaging effects and on (“1”) or off (“0”) effects of the multichannel metasurface are demonstrated. This work provides new ideas for the design of tunable metasurfaces and promotes the application of metasurfaces in THz dynamic imaging.     

Effects of Poly(Propylene Oxide)–Poly(Ethylene Oxide)–Poly(Propylene Oxide) Triblock Copolymer on the Gelation of Poly(Ethylene Oxide)–Poly(Propylene Oxide)–Poly(Ethylene Oxide) Aqueous Solutions

Poly(ethylene oxide)-poly(propylene oxide)–poly(ethylene oxide) ((EO)_n–(PO)_m–(EO)_n) block copolymers, commercially available as Pluronics (BASF Corp.) and Poloxamers (ICI Corp.), have been widely applied in medicine, biochemistry, and other fields because of their ability to form reversible micelles and physical gels in aqueous solution. Generally, for PEO–PPO–PEO block copolymers with higher ethylene oxide concentration, the micellization and gelation in aqueous solution are easier. However, if we introduce the reverse block copolymer PPO–PEO–PPO into PEO–PPO–PEO aqueous solutions, the micellization and gelation of the system will be more complex. In this work, the reverse block copolymer PO₁₄–EO₂₄–PO₁₄ (17R4) was added to the Pluronics EO₂₀–PO₇₀–EO₂₀ (P123), EO₁₀₀–PO₆₅–EO₁₀₀ (F127), and EO₁₃₃–PO₅₀–EO₁₃₃ (F108) aqueous solutions with different molar ratios. The rheological properties of different mixtures were measured to study the additive effect on the gelation behavior. The sol–gel transition temperature of the P123, F127, and F108 solutions shifted to a higher temperature when 17R4 was added to the solutions. In addition, the existence of 17R4 greatly affected the stability of gels. These results help to better understand the gelation of Pluronic aqueous solutions.     

Non-uniform Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) state

We provide a general review of the properties of the non-uniform superconducting Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) phase. Special emphasis is made on the orbital and crystal structure effects which may result in the quantum transitions between the higher Landau level states and should be responsible for the strong modification of the anisotropy of the critical field. The FFLO-type instability may be also expected in ultracold Fermi gases. In these systems it is caused not by the Zeeman interaction but by the tuning of the population imbalance between two lowest hyperfine states of the atoms. We also briefly discuss their properties.     

Annular Multi-Tip Field Emitters with Metal–Fullerene Protective Coatings

Technical Physics - A technology of creation of annular silicon field emitters with bilayer metal–fullerene coating has been developed and their performance has been studied. It has been...     

The Crystallography of Interphase Boundaries Between Silicon Carbide and Silicon Nitride in Silicon Nitride—Silicon Carbide Particulate Composites

Interphase boundaries between 3C SiC grains and two different -Si₃N₄ morphologies in Si₃N₄–SiC composites have been studied by transmission electron microscopy. In general, boundaries between small -Si₃N₄ intragranular precipitates and surrounding SiC grains were relatively free of intergranular films, whereas boundaries between large -Si₃N₄ grains and adjacent SiC grains were invariably covered with thin intergranular films. Orientation relationships approximating to [110] 3C SiC [0001] -Si₃N₄ and (001) 3C SiC (10 0) -Si₃N₄ were found to dominate between 3C SiC grains and the intragranular -Si₃N₄ precipitates, but there was no evidence of any favoured orientation relationship between the large -Si₃N₄ grains and adjacent SiC grains. The rationale for special orientation relationships arising when there is no intergranular film present at 3C SiC–-Si₃N₄ interfaces is explored geometrically using the near-coincidence site lattice model, with the significant result that the dominant orientation relationships between 3C SiC grains and the intragranular -Si₃N₄ precipitates have low misfits relative to all other possible orientation relationships between 3C SiC and -Si₃N₄.